That is soap in his mouth. He cussed, and that was (is?) a popular form of punishment at that time. I think he is describing the different subtle tastes of each brand of soap he's been punished with in that scene.
I remember seeing the original at the theater, and, for those have only seen it on TV or the newer DVD stuff, it's been editited quite a bit here and there (for example, the father did not say stuff like "Son of a gun" in the original). And the flag pole scene had me covering my mouth for almost the rest of the movie.
It's almost the season to put up the bunny pajamas picture is'nt it?
